Sunless tanning method and apparatus

ABSTRACT

Apparatus for simulating skin tanning comprises a receptacle containing a fluid comprising dihydroxyacetone, a receptacle containing a fluid comprising an amino acid, and dispensing means for simultaneously or sequentially providing desired amounts of dihydroxyacetone and amino acid.

The present application is the U.S. national application correspondingto International application No. PCT/US94/03258, filed Mar. 30, 1994 anddesignating the U.S., which PCT application is in turn a continuation ofU.S. application Ser. No. 08/040,804, filed Mar. 31, 1993 now abandonedthe benefit of which applications are claimed pursuant to the provisionsof 35 U.S.C. 120,363 and 365 (C).

FIELD OF THE INVENTION

This invention relates to apparatus useful in the simulated tanning ofskin. More particularly, the invention relates to apparatus used in thetreatment of skin with dihydroxyacetone compositions, to form a brownishcoloration thereon.

INTRODUCTION TO THE INVENTION

It has long been known that certain compounds form pigments when appliedto the skin. Products containing dihydroxyacetone (frequently simplyabbreviated "DHA") have been marketed since the early 1960's, and havebeen found satisfactory by many persons who wish to give their skin theappearance of an attractive tan, but do not desire to risk the nowwell-appreciated health hazards of exposure to solar orartificially-generated ultraviolet radiation.

However, some persons have not obtained the desired results from DHAapplications. A small number of individuals develop a coloration whichtends to appear yellowish or orange. Some others, probably due toperspiration, rubbing or washing during the slow generation of color asskin components react with DHA, or to a lack of care to evenly apply theDHA, develop uneven coloration. Many users of the available productswould prefer to obtain a more rapid generation of color.

The chemistry of DHA-skin interaction has been investigated by severalworkers. Wittgenstein and Berry published a paper "Reaction ofDihydroxyacetone (DHA) with Human Skin Callus and Amino Compounds," inThe Journal of Investigative Dermatology, Vol. 36, pages 283-286 (1961),describing work to characterize the browning phenomenon. They reportedthat DHA reacts with a number of compounds, including ammonia and aminoacids, to form a brown color, and theorized that skin browning is due tothe reaction of DHA with free amino groups in the skin, the amino groupsprobably being on arginine molecules which are present in skin proteins.

A. Meybeck published "A Spectroscopic Study of the Reaction Products ofDihydroxyacetone with Aminoacids" in Journal of the Society of CosmeticChemists, Vol. 28, pages 25-35 (1977), and characterized brown pigmentsformed from the reaction of DHA with amino and other acids at 100° C.Further experiments at 37° C. were conducted to better simulatereactions which may occur in the skin: DHA was reacted with the aminoacids glycine, lysine, alanine, serine and arginine, but only glycineand lysine produced significant amounts of pigment after 24 hours. Itwas concluded that DHA must act by initially condensing with free aminoacids at the skin surface, followed by polymerization and linking toproteins in the stratum corneum, probably through lysine side chains.

A further study was reported by M. F. Bobin, M. C. Martini and J. Cotte,"Effects of Color Adjuvants on the Tanning Effect of Dihydroxyacetone,"Journal of the Society of Cosmetic Chemists, Vol. 35, pages 265-272(1984). This work involved measuring the rate of color development aftermixing DHA and various amino acids or their derivatives, andapplications of DHA and methionine sulfoxide in vivo. It was concludedthat methionine sulfoxide is a useful adjuvant to DHA, as thecombination provided rapid color development, plus a more intense andlong lasting color than would be obtained with only DHA. This result wasthought to result from the affinity of methionine sulfoxide for keratin.

Chemical Abstracts, Vol. 95, abstract 30226g (1981) summarizes a Germanpatent document (3,037,497) pertaining to dyeing skin, hair, feathers,fur, etc. by treating with a mixture of DHA and an amino acid sulfoxide.When DHA and methionine sulfoxide were applied in cream formulations,skin turned a deep brown color after three hours and the color was moreresistant to washing than that obtained with only DHA.

Black et al., in U.S. Pat. No. 3,177,120, discussed the problem ofincluding DHA and amino group-containing sunscreens together in aformulation, and concluded that only sunscreens free from amino groupsshould be used, to prevent formation of a yellow or brown color in thestorage container; color formation is also said to be accompanied byinactivation of both the DHA and sunscreen.

Diane Debrovner, in an article entitled "Bottled Sunshine," AmericanDruggist, July 1992, describes a recently introduced self-tanningproduct which is a dual-chamber tube having a DHA-containing cream onone side and a cream containing amino acids on the other. The product issaid to create a golden, rather than orange, color on the skin.

An article by Pamela Lister, "Safe Sun," in the magazine Self, May 1992,pages 134-137 and 177, describes several sunless tanning products ofvarious manufacturers, including amino acid-containing formulations.

In spite of the teachings in the art relating to the use of DHA withtypical formulations of ∝-amino acids and their derivatives, it has beenfound that color formed thereby does not have a desired substantivity,or resistance to removal by rubbing or washing. Thus, it is desired toprovide apparatus and a method for browning skin to form simulated tanshaving improved substantivity, yet having colors which closely resemblethose obtained from exposure to ultraviolet radiation.

SUMMARY OF THE INVENTION

The invention, in one aspect, provides apparatus for impartingartificial tan to skin, comprising: a receptacle containing a fluidformulation comprising dihydroxyacetone; a receptacle containing a fluidformulation comprising an amino acid; and dispensing means forsimultaneously or sequentially providing desired amounts ofdihydroxyacetone and amino acid. The invention also includes a methodfor imparting artificial tan to skin, comprising simultaneously orsequentially contacting the skin with dihydroxyacetone and an aminoacid. Further included is a composition for prompt application to skin,comprising dihydroxyacetone, at least one amino acid and a suitablecarrier.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a pouch container having twocompartments.

FIG. 2 is a cross-sectional view of a squeeze bottle having twocompartments.

FIG. 3 is a cross-sectional view of a dual-compartment tube container.

FIG. 4 is a cross-sectional view of a container having two compartmentsand a dual pump dispenser.

FIG. 5 is a cross-sectional view of a dual-compartment pressurizeddispensing container.

FIG. 6 is a graphical representation of results from an experimentdescribed in Example 5.

DETAILED DESCRIPTION OF THE INVENTION

The invention will be described with reference to the accompanyingdrawings. In the description and claims, all percentages are expressedon a weight basis, unless otherwise noted.

In accordance with the invention, there is provided apparatus forimparting a simulated tan to skin, the apparatus having separatecompartments for a formulation containing dihydroxyacetone and aformulation containing an amino acid. As previously noted in the art, itis important to prevent mixing of the active ingredients until a user isready to make a skin application, to prevent premature reaction andcolor formation. The apparatus can be configured to simultaneouslydispense the formulations, in desired amounts, or to sequentiallydispense them. If sequentially dispensed, the formulations can be mixedbefore spreading onto the skin, or can be spread in the order ofdispensing.

Referring to FIG. 1, there are shown the features of a two-compartmentpouch 10. Included is septum 12 which, in the least complex embodimentwhere the pouch comprises heat sealed layers of a thermoplasticsubstance, is merely a heat sealed seam to divide the volume of thepouch. This septum divides the volume into chambers 14 and 16. Tearingnotch 18 can be provided to facilitate removal of the top of the pouch,when it is desired to dispense formulations contained therein. Thisembodiment will be used primarily for single-use quantities, the pouchholding an appropriate quantity for application once to the whole bodyor a portion thereof, such as only the face.

As an alternative to a tearing notch, the user can simply cut off thetop of the pouch with scissors or a knife. Further, rather thandispensing the two formulations from the pouch in two streams, as wouldbe done with the configuration depicted, septum 12 can be madefrangible; applying pressure with the fingers to one side of the pouchwill rupture the septum and permit mixing of the formulations bysequentially applying pressure to the two sides, after which a singlecomposition containing both DHA and amino acid can be applied. Ofcourse, such mixing should only be conducted promptly before use.

For sequential application of the two formulations, another tearingnotch (not shown) can be provided on the opposite side of the pouch fromnotch 18, and the septum can be extended to the uppermost limit of thepouch. This will permit only one compartment to be opened by pullingabove a notch.

FIG. 2 is a view of a squeeze bottle 20, which is provided with septum22 to form two compartments 24 and 26. The bottle is conveniently formedby molding with thermoplastic substances, as is well known in the art.In a typical embodiment, threads 34 will be provided for closure with aconventional screw cap (not shown). The threads will not be needed ifthe bottle is closed by alternative means, such as a pressed on flipcap.

Preferably, gripping indentations 28 are provided, to ensure that thebottle is squeezed in locations which will apply approximately uniformpressure to the two compartments, i.e., not to a less deformable areasuch as that directly over the septum. Upon pressure application,formulations are dispensed from the compartments through orifices 30 and32.

The bottle can be used for sequential applications of DHA and aminoacid, by providing separate closures for the two orifices. As anexample, individual snap caps can be provided over the orifices. Theuser would be required to dispense an appropriate amount of a component,rub that component into the skin and, promptly or after a prescribedtime, apply the second component to the skin in a similar manner.Application of equal amounts of the components can be accomplished withsufficient accuracy by noting the lengths of dispensed fluids on theskin; the bottle can be provided with length scales marked thereon tomake this more convenient.

Referring now to FIG. 3, there is shown a cross-sectional view of acollapsible tube assembly 36 which is useful in the invention. As shown,the outer tube 38 surrounds the inner tube 40, and contents of the outerand inner tubes can be discharged through outlets 42 and 44,respectively, by squeezing the assembly. A threaded area 46 is providedfor attachment of a closure (not shown). Any desired number of outletscan be provided for the tubes and any desired type of closure can beused, the invention not being restricted to a threaded cap.

The assembly can be fabricated from any materials normally utilized fortubes dispensing medications, cosmetic materials, hygiene products suchas toothpastes, cleaning compositions and the like, subject to the usualrequirement that the materials of construction do not react withformulations contained therein to an appreciable extent during at leastthe expected storage term. Frequently used materials include metals,polymers and composites, including laminates. Typically, the assemblywill be closed at its bottom end by crimping or heat sealing, dependingupon the materials of construction. To assure that formulations aredispensed in predetermined relative amounts from the outer and innertubes, means (not shown) such as a key can be provided at the bottom ofthe assembly for uniformly collapsing the tubes; as the bottom of theassembly is wound around a rotated key, approximately the same pressurewill be applied to the two tubes.

A further apparatus is shown in cross-section as FIG. 4. In this figure,dispensing container 48 comprises bottle 50, having dividing septum 52which forms two compartments 54 having any desired geometry. Cap 56 isadapted to fit over the outlets of pumps 58, mounted to close thecompartments and which can be any of the well-known spring loaded checkvalve pumps such as are used with hand lotions and other cosmeticproducts. Pressing down on the cap causes formulations to besimultaneously dispensed from conduits 62; releasing the cap permits itto rise under pressure from springs in the pumps, simultaneouslyreloading the pumps with stored formulations through dip tubes 60.

This apparatus requires no particular care on the part of the user toobtain a correct ratio of the formulations, in cases where theformulations are to be simultaneously dispensed and applied, but permitscomplete separation of the components until dispensing. By providingseparate caps over the pumps, it would be possible to dispense theformulations at different times, should this be desired. In eitherembodiment, reproducible amounts will be dispensed simply by pressingthe cap down for its full length of travel each time, without any needfor a user to make measurements.

FIG. 5 relates to a pressurized aerosol container which can be used todispense two components simultaneously. Container 64 comprises externalshell 66, with bottom closure 68 attached; preferably, both of thesecomponents will be fabricated from metals, with the bottom closurecrimped or welded to the shell. Gas filling port 70 is provided to sealthe container after a pressurizing gas is introduced.

The container is divided by barrier 72, which is provided with one ormore perforations 74 near the bottom of the container, to equalize gaspressure in the two sections formed by the barrier. Each section has anaccordion-pleated bag 76, preferably fabricated from a plastic material,to contain a formulation, the bags each being connected to an aerosolvalve 78 which is actuated to release formulation by its depression intothe container. Cap 80 is utilized to simultaneously depress the valves,and directs formulations through conduits 82 for application to adesired area.

This apparatus has the advantages of dispensing desired relative amountsof the contained formulations without any special care on the part ofthe user, and being very simple to use. By using plastic bags to containthe formulations, the aerosol container needs not be chemicallycompatible with the formulations, and the propellant will not normallybe in contact with the formulations. Of course, costs can be reduced bychanging the design to make use of sealed compartments having pistonsdriven by gas pressure to force formulations out through the valves, butpiston sealing, compatibility of construction materials with theformulations and other considerations will complicate the productdesign. Many alternatives will be apparent to those skilled in aerosolcontainer packaging.

Another useful package for the present invention has two compartments,divided by a removable or frangible barrier. An example is thecollapsible tube of U.S. Pat. No. 2,176,923 to Nitardy, where twosubstances are separated in a tube by a transverse partition which is acollapsible disk having a central aperture; expressible plugs in theaperture are removed by applying pressure to the bottom of the tube,causing the substances to mix. U.S. Pat. No. 3,290,017 to Davies et al.is related, having a disc which can be moved from a barrier position toa mixing position in a tube by external finger pressure.

A further example is found in U.S. Pat. No. 3,608,709 to Pike, where amultiple-compartment laminated pouch is described. This pouch, whenexternal pressure is applied, will form a single compartment by breakageof the internal barrier, permitting two formulations contained thereinto mix. Other packages having frangible internal barriers are shown inthe following U.S. Pat. Nos.: 3,756,389; 4,458,811; and 4,608,043; thesecan be adapted for use in the present invention.

U.S. Pat. No. 3,809,224 to Greenwood shows another useful package,having an external clamp divider seal which can be removed to permitmixing of components stored separately when the clamp is in place.

Each of these packages having a frangible or removable barrier will besuitable for single use unit packaging only, since it will be necessaryto use the entire contents of the package promptly after the DHA andamino acid formulations are mixed, due to the previously discussedreaction.

Alternatively, the DHA formulation (e.g., in the form of a lotion) canbe provided together with a small container (e.g., a vial or pouch) ofthe amino acid. The consumer will, upon opening the package, combine theamino acid with the DHA formulation and thus prepare a mixture forrepeated applications, which will be stable during short periods ofstorage--typically not more than about one month when using the DHAlotion formulation of following Example 3, the actual storage lifedepending upon storage conditions. Preferably, the DHA formulationcontainer will be substantially clear or be provided with a clearwindow, so that color formation can be easily detected. The user will beinstructed to apply the mixed product promptly, i.e., before significantcolor generation in the container, then discard all remaining portions.

The foregoing is a description of representative packaging techniquesfor maintaining and dispensing a formulation comprising dihydroxyacetoneand a formulation comprising an amino acid. Both formulations must befluid, that is, capable of flow under the influence of gravity or amoderate externally applied pressure. Examples of useful fluidformulations are ointments, dispersions such as creams and lotions,gels, solutions, and the like, each of which (and preparative techniquestherefor) are very well known to those skilled in the formulating art.

Typically, both formulations which are to be used together will be ofthe same type, e.g., if one is a gel, the other also will be a gel tofacilitate application and mixing. However, it is not always necessaryto observe this general principle.

Amino acids which are useful in preparing the formulations of theinvention have the general formula RCH(NH₂)COOH, where R is hydrogen ora substituted or unsubstituted hydrocarbyl group, permissiblesubstituents being halogens, nitrogen-containing groups,sulfur-containing groups, hydroxy groups, carbonyl-containing groups,and the like. In general, the amount of heteroatom substitution in ahydrocarbyl group will be less than one such atom per each five carbonatoms in the group and, usually, there will be no heteroatoms, i.e., thegroup will be hydrocarbon. It should be noted that more than one aminogroup can be present in a compound; primary amino groups are notconsidered to be "heteroatom-containing" for purposes of this invention.Useful amino acids include, without limitation, glycine, alanine,valine, leucine, phenylalanine, serine, lysine, arginine, threonine,methionine and others, alone or in combination. Glycine is a presentlypreferred amino acid.

Volumes and active ingredient concentrations of dispensed formulationsshould be chosen to provide molar ratios of DHA to primary amino groupsabout 0.5 to about 14. It is generally useful to provide formulationswhich, when mixed, contain about 0.04 to about 0.12 molar concentrationsof primary amino groups, preferably about 0.06 to about 0.1 molar andmore preferably about 0.075 to about 0.085 molar. When the amino acid isglycine, the formulations generally will be used in proportions andconcentrations which produce a mixture having about 0.25 to about 0.9percent glycine, with about 0.45 to about 0.75 percent being preferredand about 0.55 to about 0.65 percent being more preferred.

If the number of moles of DHA exceed the number of moles of primaryamino groups, a portion of the DHA will remain free to react with aminogroups in the skin, increasing the substantivity of the color formed;thus, a molar excess of DHA is preferred. Although the rate of colorformation in the skin (with free amino groups present there) isconsiderably slower than that of DHA with provided amino acid on or nearthe skin surface, color formed in the skin is much more resistant toremoval by washing and abrasion. For this reason, it is preferable toestablish both the early and frequently more intense color on the skinsurface, and the more permanent but slower forming color in the skinlayers.

It has been found that pH at the time of application affects theresulting color. In general, either the DHA formulation or the aminoacid formulation should be able to establish pH values about 3 to about13 locally when applied to the skin. More preferred are values about 7to about 11, with values about 8 to about 10 being particularlypreferred with some formulations. The optimal pH for a given amino acidapplication will be somewhat dependent upon the pK_(a) of that aminoacid, and can be easily determined by applying formulations havingdifferent pH values to the skin.

To compare simulated tans created by different means, it is helpful tohave an objective, instrumental measurement of colors and intensities.Accordingly, a method has been developed using a Minolta Chroma MeterCR-200, which analyzes reflected light from a surface and gives resultsin terms of the CIE (International Commission on Illumination)tristimulus values. These values are subsequently transformedmathematically into the L* a* b* color space, wherein the magnitudes ofchanges in hue and intensity of color correspond closely with thosepercieved by the human eye.

L*, being achromatic, ranges from black (L*=0) to white (L*=100); thisterm is called "metric lightness" and is a measure of how light or darka color is, relative to a matching shade of gray. Hue is measured interms of the chromaticity coordinates a* and b*, where a* indicatesredness (a*>0) and b* indicates yellowness (b*>0). The values of a* andb* can be plotted with a* as the x-axis and b* as the y axis, to givequantitative color information: "metric chroma" is the length of a linefrom the origin (a*=0, b*=0) to the point of a sample reading, while"metric hue angle" is the angle between the a* axis and the metricchroma line. Metric chroma indicates the strength of a color response(i.e., the extent to which a color differs from its matching shade ofgray). Metric hue angle quantifies hue in degrees, with larger valuesindicating more yellow hues and smaller values indicating more red (orless yellow) hues.

The meter is used to measure natural tans with a number of subjects, toestablish a target for the appearance of tans produced by DHA reactions.In general, it is found that points on a chromaticity plot for dark tanswill have b* from about 19 to about 24, with a* ranging from about 10 toabout 14. For medium tans, b* will be about 20 to about 24, with a* fromabout 9 to about 12. For light tans, b* will be about 18 to about 20,with a* about 7 to about 10. Rather than being a point, the target coloris represented by the area on the plot where natural tans lie. Values ofmetric chroma increase steadily as tans progress from light to medium,but increase much more slowly as tans become more dark than "medium." Incontrast, values of metric hue angle overlap significantly for light,medium and dark tans, except for very dark tans which have increasedredness (decreased metric hue angle).

Metric lightness is the third required parameter for characterizingnatural tans. L* values decrease as tans become darker, a difference ofabout one unit being discernable to a trained observer. For naturaltans, L* ranges from about 47 to about 53 for dark tans, about 54 toabout 57 for medium tans and about 58 to about 64 for light tans.

The meter is also used to measure the characteristics of simulated tansobtained using only DHA applications. Several subjects are treated withan oil in water emulsion containing 5 percent DHA, with applications (2mg DHA/cm²) being made once each day for four days. After the first day,values for b* are about 13 to about 21, the a* values are about 3 toabout 8 and L* values are about 63 to about 74. After two days, b* isabout 15 to about 23, a* is about 5 to about 8 and L* is about 62 toabout 72. After the third day, b* is about 16 to about 23, a* is about 5to about 9 and L* is about 61 to about 71. After four days, b* is about17 to about 24, a* is about 5 to about 9 and L* is about 61 to about 70.The hues for all but a few of the readings are more yellowish than thetan target area, and all but a few of the readings indicate tans morelight than natural tans, even though comparable levels of metric chromaare generated. It can generally be stated that simulated tans using onlyDHA are more yellow and lighter than natural tans having similar extentsof color formation.

The following examples are provided to illustrate various aspects of theinvention, and are not to be construed as limiting the invention in anymanner.

EXAMPLE 1

A lotion containing 1.1 percent glycine is prepared from the followingingredients:

    ______________________________________                                        Component         Grams                                                       ______________________________________                                        Part A                                                                        Water             77.00                                                       Glycine           1.10                                                        Sodium chloride   0.50                                                        Glycerin          2.50                                                        Part B                                                                        Water             0.099                                                       Coloring agent    0.001                                                       Part C            1.00                                                        Preservative                                                                  Part D                                                                        Emulsifier        3.00                                                        Emulsifying wax   1.00                                                        Cyclomethicone    4.00                                                        Isododecane       8.40                                                        Benzyl alcohol    1.00                                                        Jojoba oil        0.10                                                        Aloe Vera lipoquinone                                                                           0.10                                                        Vitamin E acetate 0.10                                                        Dimethicone       0.10                                                        ______________________________________                                    

The lotion is prepared by: adding each of the Part A ingredients to thewater in listed order, and heating to about 70° C. with constant mixing;dissolving the coloring agent to the water of Part B, mixing and addingto the Part A solution; adding the preservative with mixing andmaintaining the elevated temperature; combining all of the Part Dingredients and heating to about 70° C. with mixing; and slowly addingthe heated aqueous mixture to the heated Part D minture, with rapidmixing, to form smooth emulsion. Mixing is continued until the emulsionhas cooled.

EXAMPLE 2

A lotion containing 0.88 percent glycine is prepared using the followingingredients:

    ______________________________________                                        Component        Grams                                                        ______________________________________                                        Part A                                                                        Water            76.9685                                                      Glycerin         2.50                                                         Glycine          0.88                                                         Sodium chloride  0.50                                                         Preservative     1.00                                                         Coloring agents  0.10015                                                      Benzyl alcohol   1.00                                                         Part B                                                                        Cyclomethicone   4.00                                                         Isododecane      8.40                                                         Jojoba oil       0.10                                                         Aloe Vera lipoquinone                                                                          0.10                                                         Vitamin E acetate                                                                              0.10                                                         Dimethicone      0.10                                                         Fragrance        0.25                                                         Emulsifying wax  1.00                                                         Emulsifier       3.00                                                         ______________________________________                                    

The formulation is prepared by: adding the Part A ingredients to thewater and mixing until dissolved; adding the Part B ingredients to theaqueous solution, in the listed order, with gentle mixing; mixingvigorously for about ten minutes; then separately metering the oil andaqueous phases into a high shear mixer and recirculating into theoriginal mixing vessel, to produce an emulsion having the desiredviscosity.

EXAMPLE 3

A lotion containing 7.5 percent DHA is prepared from the followingingredients:

    ______________________________________                                        Component         Grams                                                       ______________________________________                                        Part A                                                                        Water             73.20                                                       Sodium chloride   0.50                                                        Dihydroxyacetone  7.50                                                        Preservative      1.00                                                        Part B                                                                        Emulsifier        3.00                                                        Emulsifying wax   1.00                                                        Cyclomethicone    4.00                                                        Isododecane       9.40                                                        Jojoba oil        0.10                                                        Aloe extract      0.10                                                        Vitamin E acetate 0.10                                                        Dimethicone       0.10                                                        ______________________________________                                    

The lotion is prepared by heating the water to about 70° C. and addingremaining Part A components to form a solution, forming a solution ofthe Part B components at about 70° C., and very slowly adding the heatedPart A solution to the heated Part B solution, with vigorous stirring.

EXAMPLE 4

Substantivity to water rinsing indicates the water solubility of thecolor formed, water solubility being an indication of potential problemsof streaking and clothing staining from perspiration, exposure to rain,etc. A suitable test involves measuring skin color with the MinoltaChroma Meter, applying formulations to the skin, allowing color todevelop, then repeating the color measurement. A gentle stream ofluke-warm tap water is allowed to flow over the treated skin for twominutes, then the skin is dried with paper towels. A final skin colormeasurement is then taken, thirty minutes later. Values of ΔE can becalculated from the following formula:

     (L*.sub.U -L*.sub.T).sup.2 +(a*.sub.U -a*.sub.T).sup.2 +(b*.sub.U -b*.sub.T).sup.2 !.sup.1/2

where the subscripts "U" represent readings with untreated skin and thesubscripts "T" represent readings with treated skin. Thus, ΔE alwaysrepresents total color difference between treated and untreated skin.

Substantivity to rubbing is determined by the measurements of color bothbefore and after a 10×8 centimeter, 500-gram block, fitted with a towelcovering its lower surface, is pulled across the skin through fivecycles, using a back-and-forth motion. This test is conducted first withthe towel dry, giving "Dry" results in the following table, and thenwith the towel saturated with water, giving "Wet" results.

For this example, DHA and glycine formulations are applied to skinimmediately after initial readings are taken with the Minolta ChromaMeter, using 25 μl each of a DHA formulation and a glycine formulation,rubbed into a 25 cm² skin area. A period of five hours is allowed forcolor development, then readings are again taken; the difference intotal color is termed "ΔE Initial" for the tables which follow. Aftereach of water rinsing, dry rubbing and wet rubbing, measurements aremade and ΔE is again determined.

In the experiment, the "invention" product is considered to be the DHAand glycine lotion formulations of preceding Examples 1 and 3. The"commercial" product consists of DHA and glycine lotion formulationscontained in a dual-compartment dispenser of the commercially available"Spa for the Sun, The Natural Look, Self Tanner for the Face, SPF 15" byElizabeth Arden Co., New York, N.Y. U.S.A., which lists the ingredientson its label as follows:

    ______________________________________                                                FIRST COMPONENT                                                               Active Ingredients:                                                           Ethylhexyl p-methoxycinnamate                                                 Oxybenzone                                                                    Other Ingredients:                                                            Water                                                                         Cyclomethicone                                                                Propylene glycol                                                              Glycine                                                                       C.sub.12-15 alkyl benzoate                                                    Aloe Vera gel                                                                 Cetyl dimethicone                                                             Polyglyceryl ricinoleate                                                      Trihydroxystearin                                                             Lysine hydrochloride                                                          Ornithine hydrochloride                                                       Sodium hyaluronate                                                            Chamomile extract                                                             Mallow extract                                                                Rosemary extract                                                              Sambucus extract                                                              Tocopheryl linoleate                                                          Cetyl dimethicone copolyol                                                    Methicone                                                                     Sodium chloride                                                               Methylparaben                                                                 Propylparaben                                                                 Fragrance                                                                     Sodium dehydroacetate                                                         DMDM hydantoin                                                                Trisodium EDTA                                                                Titanium dioxide                                                              SECOND COMPONENT                                                              Active Ingredients:                                                           Ethylhexyl p-methoxycinnamate                                                 Oxybenzene                                                                    Other Ingredients:                                                            Water                                                                         Dihydroxyacetone                                                              Cyclomethicone                                                                C.sub.12-15 alkyl benzoate                                                    Cetyl dimethicone                                                             Polyglyceryl ricinoleate                                                      Trihydroxystearin                                                             Cetyl dimethicone copolyol                                                    Methicone                                                                     Propylene glycol                                                              Sodium chloride                                                               Methylparaben                                                                 Propylparaben                                                                 DMDM hydantoin                                                                Trisodium EDTA                                                                Iron oxides                                                                   Titanium dioxide                                                      ______________________________________                                    

The Elizabeth Arden product has been found by analysis to contain about3.72 percent glycine, about 0.1 percent lysine compounds and about 0.09percent ornithine compounds in the first component, and about 7.3percent DHA in the second component. Its dispenser deliversapproximately equal amounts of the two lotions, upon actuation.

    ______________________________________                                                  ΔE                                                            Product     Initial                                                                              Rinse      Dry  Wet                                        ______________________________________                                        Invention   4.0    3.4        4.2  3.1                                        Commercial  5.8    3.8        6.0  3.5                                        ______________________________________                                    

In the following restatement of the results, "% Color Remaining" iscalculated by the equation (ΔE_(AFTER) /ΔE_(INITIAL) ×100), where"after" values result from measurements following a particular procedureand "initial" values result from measurements taken prior to thatprocedure. Data in this table more clearly show that, although thecommercial product initially gives a more intense color than the productof the invention (as shown in the preceding table), that coloration isconsiderably more water-soluble than is the coloration from theinventive product.

    ______________________________________                                                 % Color Remaining                                                    Product    Rinse         Dry    Wet                                           ______________________________________                                        Invention  84            109    77                                            Commercial 66            108    62                                            ______________________________________                                    

EXAMPLE 5

Skin on 25 cm² areas of the inner forearms of eight subjects is treatedwith 0, 12.5, 25 or 50 μl of a glycine formulation as in Example 1(except containing 0.10015 grams of a mixture of coloring agents and0.25 grams of fragrance, and having 0.3505 grams of water deleted fromthe formulation), 25 μl of a DHA formulation as in Example 3 (exceptthat the fragrance is replaced by an equivalent weight of water), andsufficient quantities of a similar placebo lotion (containing neitherglycine nor DHA) to total 75 μl on the skin sites. Additionally, twoother 25 cm² skin sites are treated with either 0 or 50 μl of theglycine formulation, 50 μl of the DHA formulation and sufficient placebolotion to total 100 μl. Skin color is measured with the Minolta ChromaMeter before any formulations are applied.

Five hours after application, the skin sites are measured for color withthe Minolta Chroma Meter, rinsed with warm running tap water for abouttwo minutes, dried with paper towels, allowed to air dry for 15 to 20minutes, and are again measured with the meter. Values of ΔE arecalculated as in the preceding example and are shown in the followingtable. The glycine amounts shown in the table are expressed in μmolesper 25 cm² of skin area.

    ______________________________________                                        Moles DHA per      ΔE                                                   Glycine Mole Glycine   Before Rinsing                                                                           After Rinsing                               ______________________________________                                        Application Density = 3 μl/cm.sup.2                                        0       --             3.25       3.19                                        1.83    11.4           4.02       3.93                                        3.66    5.7            4.35       4.01                                        7.33    2.8            4.59       3.41                                        Application Density = 4 μl/cm.sup.2                                        0       --             3.98       3.64                                        7.33    5.7            5.31       4.04                                        ______________________________________                                    

These results are restated in the table below after subtracting the meanΔE value for the DHA-induced color (without glycine) from the precedingvalues, and calculating the percentage increase in ΔE attributablesolely to the glycine content (before rinsing) and the percent of formedcolor due to the glycine content which remains after rinsing.

    ______________________________________                                                Moles DHA per   Color   Color                                         Glycine Mole Glycine    Increase                                                                              Remaining                                     ______________________________________                                        Application Density = 3 μl/cm.sup.2                                        1.83    11.4            24      96                                            3.66    5.7             34      75                                            7.33    2.8             41      16                                            Application Density = 4 μl/cm.sup.2                                        7.33    5.7             33      30                                            ______________________________________                                    

The results from this second table are represented graphically in FIG.6. From the numerical results it can be clearly seen that, although morecolor is formed by higher amino acid levels applied with a given molarexcess of DHA, such color is primarily water-soluble. A balance must betaken between the total initial amount of color and the relativepermanence of the color; the optimal amount of glycine occurs where thetwo lines cross on the graph. Color formed by the reaction of glycineand DHA will decrease the eventual coloring formed by reaction of theDHA with skin, since less DHA will be available for the slower (but morepermanent) skin reaction.

By conducting this simple experiment, optimal concentrations for otheramino acids and desired levels of DHA can be determined.

The invention has been described with respect to several specificembodiments, but is not to be limited to those embodiments, the scope ofthe invention being defined only by the appended claims. Variousimprovements, alternatives and equivalents will be apparent to thoseskilled in the art upon reading the foregoing description and examples,and such are included within the claimed invention.

What is claimed is:
 1. Apparatus for imparting artificial tan to skin,comprising:(a) a receptacle containing a fluid formulation comprisingdihydroxyacetone; (b) a receptacle containing a fluid formulationcomprising an amino acid; and (c) dispensing means for simultaneously orsequentially providing amounts of dihydroxyacetone and amino acid whichwill establish a primary amino group concentration about 0.04 to 0.12molar in a mixture of the formulations.
 2. The apparatus of claim 1,wherein at least one of dihydroxyacetone and amino acid is present in asolution.
 3. The apparatus of claim 1, wherein at least one ofdihydroxyacetone and amino acid is present in an emulsion.
 4. Theapparatus of claim 1, wherein at least one of dihydroxyacetone and aminoacid is present in a gel.
 5. The apparatus of claim 1, wherein thedispensing means provides about 0.06 to about 0.1 molar primary aminogroup in the mixture.
 6. The apparatus of claim 5, wherein thedispensing means provides about 0.075 to about 0.085 molar primary aminogroup in the mixture.
 7. The apparatus of claim 1, wherein the molarratio of dihydroxyacetone to primary amino group is at least about
 1. 8.The apparatus of claim 1 wherein at least one formulation establishes pHvalues about 3 to about 13, when desired amounts of the formulations aremixed.
 9. The apparatus of claim 8, wherein pH values about 7 to about11 are established.
 10. The apparatus of claim 8, wherein pH valuesabout 8 to about 10 are established.
 11. The apparatus of claim 1,wherein the amino acid has the formula RCH(NH₂)COOH, in which R ishydrogen or a hydrocarbyl group.
 12. The apparatus of claim 1, whereinthe amino acid is glycine.
 13. The apparatus of claim 12, wherein thedispensing means provides about 0.3 to about 0.9 percent glycine in themixture.
 14. The apparatus of claim 12, wherein the dispensing meansprovides about 0.45 to about 0.75 percent glycine in the mixture. 15.The apparatus of claim 12, wherein the dispensing means provides about0.55 to about 0.65 percent glycine in the mixture.
 16. A method forimparting artificial tan to human skin, comprising contacting the skinwith a formulation containing dihydroxyacetone and a formulationcontaining an amino acid having the formula RCH(NH₂)COOH, wherein R ishydrogen or a hydrocarbyl group, the formulations when mixed containingabout 0.04 to about 0.12 molar primary amino group.
 17. The method ofclaim 16, wherein the dihydroxyacetone and amino acid are applied toskin sequentially.
 18. The method of claim 16, wherein thedihydroxyacetone and amino acid are applied to skin substantiallysimultaneously.
 19. The method of claim 16, wherein a formulationcontaining dihydroxyacetone and amino acid is applied to skin.
 20. Themethod of claim 16, wherein pH values between about 3 and about 13 areestablished as skin is initially contacted.
 21. The method of claim 20,wherein pH values between about 7 and about 11 are established.
 22. Themethod of claim 20, wherein pH values between about 8 and about 10 areestablished.
 23. The method of claim 16, wherein the concentration ofprimary amino group is about 0.06 to about 0.1 molar in the mixture offormulations.
 24. The method of claim 16, wherein the concentration ofprimary amino group is about 0.075 to about 0.085 molar in the mixtureof formulations.
 25. The method of claim 16, wherein the amino acid isglycine.
 26. The method of claim 25, wherein the concentration ofglycine is about 0.3 to about 0.9 percent in the mixture offormulations.
 27. The method of claim 25, wherein the concentration ofglycine is about 0.45 to about 0.75 percent in the mixture offormulations.
 28. The method of claim 25, wherein the concentration ofglycine is about 0.55 to about 0.65 percent in the mixture offormulations.
 29. A composition for prompt application to skin,comprising a mixture of:(a) a formulation containing dihydroxyacetone;and (b) a formulation containing an amino acid having the formulaRCH(NH₂)COOH, wherein R is hydrogen or a hydrocarbyl group;thecomposition having a primary amino group concentration about 0.04 toabout 0.12 molar.
 30. The composition of claim 29, wherein theconcentration of primary amino group is about 0.06 to about 0.1 molar.31. The composition of claim 29, wherein the concentration of primaryamino group is about 0.075 to about 0.085 molar.
 32. The composition ofclaim 29, wherein the amino acid is glycine.
 33. The composition ofclaim 32, wherein the concentration of glycine is about 0.3 to about 0.9percent.
 34. The composition of claim 32, wherein the concentration ofglycine is about 0.45 to about 0.75 percent.
 35. The composition ofclaim 32, wherein the concentration of glycine is about 0.55 to about0.65 percent.